Railyway sleepers

ABSTRACT

A dimensionally stable combination of wood and inorganic material is provided as railway sleepers or ties. The wood is preferably a softwood impregnated with an alkali-metal or alkaline earth-metal silicate solution, which has been rendered water insoluble after impregnation. Preferably sodium silicate (water glass) is used as the solution. Any cracks, gaps, shakes, splits, or the like, remaining after impregnation are filled so as to deny entry of water, ice, snow, and debris into such cracks, etc. Predrilled holes in the ties receive deeply threaded railway spikes, capped by a hexagonal cap to hold the rails. Preferably, the spikes and caps are coated with a similar solution to provide both corrosion protection and strong bonding of the components.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to dimensionally stable, insect resistant, combinations of wood and inorganic material, more specifically, wood impregnated and/or coated with an alkali- or alkaline earth-metal silicate, which silicate has been polymerized subsequent to impregnation/coating. For convenience hereinafter, “impregnation” means coating and/or impregnation. The wood article (combinations of wood and inorganic material) is dimensionally stable over a wide range of environmental conditions of temperature, humidity, sunlight exposure, and other environmental conditions making it an acceptable basic material throughout the world. Particular utilities are as railway sleepers (sometimes also known as railway ties).

2. Description of the Related Art

The use of wood as a railway sleeper or tie has a long history in the United States. Historically, the wood used was an American hardwood, primarily oak. However, the prior art railway ties were prone to degradation from the environment, primarily insect infestation, mildew and rot. Attempts to treat the wood tie to ameliorate these defects included, among others, coating and/or impregnating the tie with organic materials, such as creosotes of various types (e.g., coal-tar creosote, crystal-free coal-tar creosote) anthracene oils, or copper-, or copper compound-, containing substances. See generally Handbook No. 72, U.S. Department of Agriculture, Forest Products Laboratory, Forest Service, 1955, pp. 399-409 (herein incorporated in its entirety by reference). While a slight improvement in delaying the onset of insect infestation, mildew and rot, these prior art ties also eventually failed. Evidence of failure can be visually apparent, such as the rotting of a tie, or may take more subtle form, such as loosening of the fasteners to hold the rails to the ties. Furthermore, even though wood ties have an excellent response to the ballast forming the railway beds, the wooden ties of the prior art are not dimensionally stable. It has been estimated by the inventor that a typical oak tie will lose on the order of 100 pounds (45.45 kilograms), primarily due to loss of entrained moisture. This loss results in a reduction of the dimensions of the tie, resulting in shrinkage away from the ballast of the railway bed. Another defect in wood based ties is that all wood, being a natural material, has defects in the form of voids formed by cracks or splits in the wood surface. These cracks and splits permit foreign materials, such as ice and snow to enter these voids. The ice and snow, upon melting and refreezing, can open up the voids, making the cracks and splits larger than naturally occurring. As a result of this process, or sometimes even in the absence of this process, other foreign materials, such plant seeds, flakes of the ballast, ballast aggregate itself, and other foreign matter can take residence in the voids created by the cracks and splits. This foreign matter works its way deeper into the void, opening up the crack and splits, further weakening the tie and the integrity of the fasteners anchoring the rails to the tie. This weakening means not only that the rails are not held firmly to the ties by the fasteners, resulting in tie plate slapping, permitting the rails to move independent of the ties, but also that due to shrinkage, the tie is no longer fully supported by the ballast and can move, not only in an upward and downward direction, but also axially along the length of the rail direction. The shrinkage can also cause a void beneath the tie, i.e., beneath the tie and its supporting ballast, such that the shrunken tie is no longer firmly supported by the as placed ballast. In a typical railway bed, many of these conditions are occurring simultaneously such that it is not often easy to determine the cause of a derailment due to one or more of these defects contributing to a derailment. Even if derailment has not yet occurred, the failure to adequately anchor the rail to the sleeper and the sleeper to be firmly supported by the ballast leads to premature wear on the rails, the rolling stock and a loss of fuel efficiency due to the undesired nature of rail and railway car movement over an unstable tie.

The art attempted to correct these problems by abandoning wood ties altogether and going to composites of concrete with embedded or interior metal reinforcement. Even so, these non-wood ties do not form a suitable base on which to anchor the rails for several reasons. Firstly, the concrete ties are not held as firmly by the ballast of a rail bed as are wood ties, permitting the ties to rise and fall every time load is applied through the rail to the tie, such as by a wheel of a passing railway train entering directly over the tie and exiting into the space between ties. This upward and downward motion, repeated many times during a single traverse of a railway train, causes localized failure of the concrete ties, especially in the fasteners holding the rails to the ties, thereby loosening the rails, possibly to an extent to cause derailment. The localized failure is caused by cracking, chipping and/or flaking of the concrete tie in the vicinity of the fasteners, such that the rails are no longer fixed in the as set dimension when first installed.

Thus, there is a long standing need to provide a material suitable for use as a railway tie or sleeper, having all the attributes of wood, but without the detriment inherent in such a material.

OBJECTS OF THE INVENTION

It is a principal object of this invention to provide a new form of railway tie which avoids the defects of prior art ties.

It is a further object to provide dimensionally stable railway ties which are resistant to insect infestation, mildew and rot.

It is a still further object to provide wood-based composite railway ties, without surface cracks or splits into which foreign matter might enter.

It is another object of the invention to provide improved anchoring of the rails to the ties of the invention.

It is a still further object of the invention to provide improved railway beds resistant to derailment caused by ballast, tie or rail anchoring failures.

it is a principal object of this invention to improve railway safety by ameliorating causes of derailment.

It is a further object to increase the fuel efficiency of rolling stock by avoiding the inefficiency of travel over a railway bed.

It is still a further object of the invention to reduce the frequency in which railway beds have to be rebuilt and/or maintained.

These and other objects will become apparent in connection with reading the detailed description of the preferred embodiments in conjunction with the appended drawings.

SUMMARY OF THE INVENTION

A new form of railway tie is disclosed herein comprising a composite wood/inorganic material. The wood tie is devoid of sites where rain/snow/debris can enter beneath the surface of the tie. Although the ties can be sold as an “as-manufactured” material, it is within the scope of the invention in further attaching, at the site of manufacturing, pre-placed metal fasteners in the composite ties per the customer's specification or in standard format.

It is also within the scope of the invention to provide safer, improved, energy efficient railway beds comprising the ties of the invention in combination with rails and ballast. To be perfectly clear, methods of manufacture of the ties and methods of use of the manufactured ties, as well as the resultant manufactures are contemplated as part of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a typical railway tie of the Prior Art;

FIG. 2 is a schematic illustration of the wood and inorganic material tie of the invention formed by impregnating wood with an inorganic material and polymerizing the inorganic material, in situ;

FIG. 3 is a schematic representation of a railway tie according to the invention with existing surface cracks or splits filled with materials preventing the entry of foreign materials;

FIG. 4 is a typical railway bed of the prior art formed by installing the Prior Art ties of FIG. 1 in a ballast.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a wood tie 10 according to the prior art. Tie 10 has a plurality of surface voids at 12-16, into which foreign matter (not shown) can enter. This foreign matter can enlarge the size and shape of voids 12-16. Tie 10 also contains a split 11 traversing from a top face 20 of the tie 10 to an end face 25, as shown in FIG. 1. Side face 22, as well as the opposing face (not shown) of tie 10 may also contain cracks and splits. Furthermore, tie 10 can be subject to loss of as much as 100 pounds (45.45 kilograms) of moisture after being placed in a ballast 50 (FIG. 4). This is typical of an American hardwood, such as oak, but will differ according to the type of wood and processing conditions to which such wood is subject. This shrinkage creates voids 40, 41, 42 beneath the Prior Art ties 10, as well as voids along 43, 44, 45 between the side faces of ties 10 and ballast 50.

FIG. 2 shows wood tie 30 having voids 32-35 and split 31, as in the wood tie 10 of the Prior Art (shown in FIG. 1). However, tie 30 has been impregnated by an inorganic material which has been polymerized in situ, encapsualating the wood fibers and any voids between the wood fibers. However, the encapsulating material is not of a nature that it can fill the voids 32-35, nor split 31.

I prefer to use American softwoods, which are less expensive than the American hardwoods such as oak. Softwoods are also known as conifers, because all United States native species of softwoods bear cones of one type or another (Source, Handbook No. 72, id., p 5.). A preferred American softwood includes Southern Yellow Pine. As shown in FIG. 2, the end face of the tie 30 is covered in the polymerized inorganic compound, as are all the other faces (not shown for clarity) and the interior (not shown) of the tie 30.

As the inorganic compound, I prefer soluble alkali- or alkaline earth metal silicate solutions. Most preferred are sodium silicate solutions (also known as water glass) which can be polymerized when impregnated into the wood and subjected to energy application, such as heat or radiation energy. The application of heat can be applied in various modes, such as in a convection oven, by radiant heaters, hot air flow, and similar methods. Radiation energy can be supplied by gamma rays, radio frequency irradiation, infrared radiation, etc. I prefer microwave radiation.

In order to enhance the penetration of the solution into the wood, between the wood fibers and even into the cells of the wood, I may optionally subject the wood to the application of an evacuated atmosphere (a vacuum) for up to 30 minutes or longer. The length of time of vacuum application depends on various parameters, including but not limited to the amount of wood being processed, the size of the chamber being evacuated, the temperature of the wood, the moisture content of the wood, preprocessing conditions, such as kiln drying, storage, and harvesting technique. In some situations, I have found it acceptable to subject the wood to a vacuum of −29.975 mm Hg for 30 minutes.

The impregnation can also occur at elevated parameters of pressure. The soluble silicate solution can be administered under elevated pressures ranging from 50-500 psi, preferrably 50-300 psi, 50-200 psi, or alternatively, 200-500 psi.

I have sometimes found it beneficial to alternate the vacuum and pressure application steps a number of times in impregnating a tie. Typical processing would be vacuum application for a period of time, followed by pressurized application of the soluble alkali- or alkaline-earth metal solution for a second period of time, and then repeating the complete cycle of alternating vacuum and pressure application once, twice or thrice, before applying the energy necessary to polymerize the solution and convert it into an insoluble form.

The concentration of the soluble silicate in the solution can also vary depending on the type of wood being impregnated, the harvesting and storage history of the wood, the preprocessing conditions, such as kiln drying, or the absence thereof, the degree and duration of vacuum administration, if applicable, the type of alkali- or alkaline-earth metal silicate used, etc. I have found concentrations of 0.04-600 g Na₂SiO₂/kg water are suitable.

Under the foregoing conditions, I have been able to penetrate not only the space surrounding the fibers of wood but also the cellular walls of a wood sample and deposit polymerized, insoluble alkali- or alkaline earth metal silicate, such as sodium silicate, throughout a wood tie.

The resultant tie 30 is completely coated on its surface and impregnated in its interior as to render it dimensionally stable, preventing a dimensional change due to loss of entrained moisture, is resistant to insect infestation, substantially impervious to the elements, including water, ice and snow. However, the impregnation process will not fill the voids 32-35 nor crack 31 therein, although the walls of the voids will be impervious to the elements.

In a further embodiment of the invention, as illustrated in FIG. 3, the cracks 32-35 and split 31 of the tie 30 of FIG. 2 are filled so as to prevent the entry of foreign materials, such as water, ice, snow, seeds, flakes and pieces of ballast, among others, from entering the voids, and subsequently enlarging the voids and resultant weakening of the tie 30. It is important to at least fill the cracks in the upper surface 50 and in surface 52, as well the surface opposing surface 52, (not shown).

FIG. 3 shows a filling substance placed into each of cracks 32-35 and split 31. This filling substance adheres to the walls of these voids, bonding thereto in both a chemical and mechanical fashion. The voids are preferably filled so as to be flush with the surface or forming a slightly convex protrusion above the surface. As shown in FIG. 3, a filling substance 60-64 is placed into cracks 34, 35, 36, 33, respectively and into split 31 as filling substance 64.

The filling substance 60-64 is any suitable material that will assure a good, long term bond to the walls of the voids.

I have found that a paste of calcium powder mixed with an alkali-metal silicate to form a slurry can be made to sufficient consistency to fill the gaps, shakes, splits, cracks, or the like inherent to wood and to bond with the alkali-, or alkaline-earth metal silicate, such as sodium silicate that have been infused into the wood, sufficient to form a bond with the wood, infused alkali-metal silicate and the void filler material 60-64 becomes an essentially insoluble calcium silicate precipitate.

Similarly, the paste may be any calcium materials capable of forming a slurry.

Similarly the alkali- or alkaline earth metal silicate may be combined with other metals, or combinations of metals, or their alloys, such as ferric, ferrous, aluminum, and other mineral combinations, and any materials capable of forming complexes with alkali- or alkaline-earth metal silicate to form a wide variety of alkali- and alkaline-earth metal complexes capable of bonding to the silicate already infused into the wood.

Alternatively, the cracks and splits may be filled with any glue, resin, with or without wood or sawdust or other fillers therein, capable of forming substantially insoluble materials. Among the resins, epoxies are preferred.

Alternatively, the cracks and splits can be filled with any glue or resin, with or without wood, sawdust, or other fillers, capable of forming a stable, even if soluble or partially soluble material, provided the material is protected by a water impermeable coating.

Although I have illustrated the filler being applied after infusing and impregnation of the tie 30, it is to be expressly understood that the filler may be applied before, after or during infusion of the soluble silicate. The order and combination of steps may be performed in any order in order to achieve the desired result.

A further aspect of the invention involves the predrilling of holes to receive a threaded railway spike.

Although it is to be understood that the ties of the invention may be manufactured for sale without any holes drilled therein, in a preferred embodiment, holes are predrilled part way into the tie for the purpose of receiving a threaded shaft of a railway spike with a midway stop/grip that prevents the spike from backing out, once installed. The hole, predrilled into the tie, at the appropriate places determined by standard or a custom specification, are sufficiently narrow to bind the shaft of the spike extremely tightly without splitting or cracking the tie. It is preferred that no additional holes be drilled.

The portion of the spike shall extend at least two inches beyond the surface of the tie, and shall be deeply grooved/threaded having an internal diameter approximately ⅔ of the diameter of the spike shaft that is embedded in the tie and an outer diameter that is equal to the outer diameter of the embedded portion of the spike shaft.

In a further embodiment of the invention, the creation of a railway bed, using the tie 30 is envisioned. Once the ties are placed at the desired location, and the rails and tie plates are in place, a hexagonal threaded metal cap having threads with an inner diameter matching the deeply grooved shaft, and an outer diameter extending at least 1.5 inches (3.8 cm) than the outer diameter of the shaft of the wood embedded portion of the threaded spike, said metal cap having a height at least 1 inch (2.54 cm), forming a large, heavy metal hex ring suitable for tightening with industrial equipment. The hex ring may either have an open top or a solid metal top extending over the shaft of the spike.

Optionally, before, or after, installation, the metal spike and hex ring shall be coated with an alkali-metal or alkaline-earth metal silicate as corrosion protection, and to facilitate chemical bonding of the metal components with the impregnated tie 30. One benefit of this embodiment of the invention is the formation of an extremely strong, stable, and more permanent system of tie, spike, tie plate and rail that dissipates stresses more evenly throughout the system. An additional benefit of this embodiment is ease of tightening at the top of the tie; that eliminates slippage along the spike shaft; that eliminates tie plate slapping; and also eliminates corrosion of spike shaft and hexnut attachment, and removes spike kill, one of the most serious problems of railway ties.

The process of making dimensionally stable combinations of wood and inorganic material mentioned herein also increases the strength of the wood. Therefore, in addition to the benefits envisioned for wood ties, the process can eliminate sheathing undelayments in home construction, as in a subfloor, if the floor is made according to the disclosed method, or subwalls, if the siding is made according to the disclosed process. Fencing can be made in approximated ⅓ the thickness of conventional fencing while demonstrating equivalent strengths. As the disclosed process eliminates shrinking and swelling in wood products, wood “bricks” and “brick” veneer can be made by coating the dimensionally stable, product combinations of wood and inorganic material made by the disclosed process, with a mineral aggregate or coating of fine mineral particles. The coating can optionally be textured to simulate the appearance of real brick. The resulting products will be much lighter than conventional bricks, but will look like brick and have the texture of brick. The dimensionally stable wood products can be used as an underlayment for light duty bridges and roadways. For example, the sand/aggregate of a roadway can be replaced by thick planks of the composite wood made according to the invention and covered with concrete or asphalt to make the roadway.

Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.

The reader's attention is directed to all papers and documents which are filed concurrently with this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All the features disclosed in this specification (including any accompanying claims, abstract, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 

I claim:
 1. A railway sleeper formed of a dimensionally stable combination of wood and an impregnated alkali- or alkaline earth metal silicate which silicate has been rendered water insoluble.
 2. The railway sleeper of claim 1, wherein the silicate is sodium silicate.
 3. The railway sleeper of claim 1, wherein the wood is selected from the group consisting of softwoods.
 4. The railway sleeper of claim 1, wherein the wood is Southern Yellow Pine.
 5. The railway sleeper of claim 1, wherein surface voids in the sleeper are filled with a paste of calcium powder mixed with an alkali-metal silicate.
 6. The railway sleeper of claim 1, wherein surface voids in the sleeper are filled with a water insoluble material, optionally containing a filler.
 7. The railway sleeper of claim 6, wherein the insoluble material is selected from glue and resin.
 8. The railway sleeper of claim 6, wherein the filler is present and is one selected from the group consisting of wood and sawdust.
 9. The railway sleeper of claim 1, wherein surface voids in the sleeper are filled with a water soluble or partially soluble material that is coated with a water insoluble material.
 10. A process of making a railway bed comprising installing the railway sleeper of claim 1 on a railway bed and attaching rails to the sleeper.
 11. The process of claim 10, wherein the sleeper is provided with factory installed railway spikes extending above a top surface of the sleeper.
 12. The process of claim 11, wherein the railway spikes are deeply threaded and are installed in holes drilled partially into the sleeper during manufacture of the sleeper.
 13. The process of claim 12, wherein the portion of the railway spike extending above the surface of the sleeper is engaged by a hexagonal shaped threaded cap.
 14. The process of claim 13, wherein the threaded cap and spike are coated with an alkali- or alkali-metal silicate.
 15. The process of claim 14, wherein the silicate acts as both a bonding agent and corrosion inhibitor.
 16. A railway comprising a plurality of the railway sleepers of claim 1, the sleepers supporting rails installed on the sleepers and a ballast beneath and between adjacent sleepers. 